11 Medications that may cause memory loss

11 Medications that may cause memory loss
April 7, 2014 10:37 AM

If one is increasingly forgetful or if one is having memory problems in his/her daily life then most likely he/she is suffering from a problem of “memory loss”. Memory loss can be either short-term or long-term. Short-term memory loss is forgetfulness of recent events while long-term memory loss is inability to retain memories that should be retained anywhere from a few days to the rest of life.

Most people consider memory loss as a sign of aging, but this is not always true. Aging is one of the causes, not the only cause of memory loss. Memory impairment can also occur due to side effect of some medications. One must be wise to choose a thing by comparing its effects versus side effects.

There are a number of medicines that can lead to memory loss; some of them are listed as follows.

1. Anti-anxiety drugs

Examples: Alprazolam (xanax), clonazepam (klonopin), diazepam (valium), lorazepam (ativan), and flurazepam (dalmane).

Why are they prescribed?

Benzodiazepines are anti-anxiety drugs. These drugs enhance the effect of neurotransmitter gamma amino butyric acid on their respective receptors, resulting in sleep-inducing, anti-anxiety, anticonvulsant, euphoric, sedative and muscle relaxant effects. They are useful in treating agitation, anxiety disorders, muscle spasms, seizures and delirium. They can also be helpful in treating insomnia and depression.

How do they cause memory loss?

Benzodiazepines suppress activity in key parts of the brain, including those critical parts involved in the formation of memory and memory transfer. Due to interference with these important areas they can dampen the transfer of data from the short-term memory to long-term memory. Interestingly, this side effect of benzodiazepines is taken as a plus point by anesthesiologists. To avoid problems of memory loss these drugs should be used only for a short duration especially in elders.

2. Cholesterol-lowering drugs

Examples: Lovastatin (mevacor), atorvastatin (lipitor), pravastatin (pravachol), fluvastatin (lescol) and simvastatin (zocor).

Why do we use these drugs?

Statins are the cholesterol lowering drugs. These drugs reduce cholesterol biosynthesis as well as modulate lipid metabolism. They are used to treat high cholesterol levels. These drugs mainly lower the cholesterol in blood, however, may also lower in the brain.

How statins can lead to memory impairment?

One quarter of the total body’s cholesterol is present in the brain. Lipids are necessary and vital for the formation of connections between nerve cells and serve as a link to memory and learning. As statins lower brain levels of cholesterol, they can lead to memory impairment and loss. A study published in 2009 in pharmacotherapy journal found that three out of four people taking cholesterol lowering drugs experience cognitive effects. So, for mild elevation of cholesterol one should avoid statins. Instead, a combination of vitamins (B12, B6 and folic acid) may be taken.

3. Tricyclic Antidepressants

Examples: clomipramine (anafranil), trimipramine (surmontil), amitriptyline (elavil), desipramine (norpramin), imipramine (surmontil), doxepin (sinequan) and nortriptyline (pamelor).

What are these drugs normally used for?

Tricyclics are the anti-depressant drugs. They affect neurotransmitters (naturally occurring chemical messengers). They block the absorption of the neurotransmitter serotonin and norepinephrine increasing the availability of these chemicals in the brain. This helps brain cells in sending and receiving messages which in turn elevates mood. Tricyclic antidepressants are normally used for depression, anxiety disorders, chronic pain, eating disorder, obsessive compulsive disorders, smoking cessation, menstrual cramps and hot flashes.

How memory loss can occur with these anti-depressants?

Serotonin and norepinephrine are the brain’s key chemical messengers. As tricyclics block these neurotransmitters they can cause memory problems, disorientation and confusion. This effect of tricyclic antidepressants is dose related i.e. high dosage can lead to more memory impairments. A research showed that tricyclic causes memory impairments in 35% of people and difficulty in concentrating in 54% of people. To avoid this effect lower dose of these drugs should be used and fewer side effects, causing tricyclic (venlafaxine) should be used.

4. Anti-seizure drugs

Examples: carbamazepine (tegretol), acetazolamide (diamox), gabapentin (neurontin), lamotrigine (lamictal), ezogabine (potiga), oxcarbazepine (trileptal) etc.

Why are anti-seizures prescribed?

Seizure is an abnormal electrical activity in the brain. Anti-seizure drugs decrease membrane excitability by interacting with neurotransmitter receptors or ion channels. They dampen the flow of signals within the brain and in this way they limit seizures. They are effective in treating seizures, bipolar disorder, mood disorders and mania.

Why do anti-seizures cause memory loss?

All drugs that dampen the signals or flow of signals in the brain can cause memory loss. It is mentioned in the above paragraph that anti-seizures are among one of those that depress signaling so they can also lead to memory impairment.

5. Narcotic painkillers

Examples: fentanyl (duragesic), morphine (astramorph), hydrocodone (norco), oxycodone (oxycontin), and hydromorphone (dilaudid).

Why are these drugs used?

Narcotic painkillers are known as opioid analgesics. As their name indicates they are used for acute and chronic pain of moderate to severe nature. Codeine and hydrocodone are helpful in relieving cough. They are also used just before or during surgery.

How memory loss can occur with narcotic painkillers?

Narcotic analgesics work by stemming the flow of pain signals within the central nervous system and by blunting one’s emotional reaction to pain. These two actions of narcotic painkillers are mediated by those neurotransmitters that are also involved in memory. Due to this they can interfere with short-term and long-term memory. When narcotics are used for an extended period of time, chances of memory loss increase many folds.

6. Sleeping aids (Non benzodiazepines sedative-hypnotics)

Examples: Zaleplon (sonata), zolpidem (ambien), eszopiclone (lunesta).

Why are these drugs normally prescribed?

Normal sleep is necessary for fresh, relaxed and energetic start of the day. Any alteration in normal sleep makes a person very tired and stressful. This alteration induces in a need to take the help of sleeping pills. Sleeping pills help to treat insomnia and other sleep disorders. They are also helpful in mild anxiety. They help treat sleep problems by increasing sleep time and decreasing sleep latency.

How do they cause memory loss?

Like benzodiazepines, these drugs bind to gamma amino butyric acid receptors, leading to inhibition of neuronal excitation. They decrease activity in some parts of the brain and can restrict the interaction between short-term and long-term memory by their affect on parts involved in memory transfer. They can also cause a state of forgetfulness called as amnesia and can elicit strange behaviors such as driving a car, walking or cooking in sleep with no memory of the event upon awakening. Long term use of these medicines induces a state of dependence and addiction in one and makes withdrawal of these drugs very difficult.

7. Anti-hypertensive drugs (beta-blockers)

Examples: atenolol (Tenormin), carvedilol (Coreg), metoprolol (Lopressor, Toprol), propranolol (Inderal), sotalol (Betapace), timolol (Timoptic) etc.

What is the use of these drugs?

Beta blockers are one of the groups of anti-hypertensive medicines. They slow down the heart rate and blood pressure. These drugs are usually prescribed in the treatment of high blood pressure. They can also help in the management of congestive heart failure and abnormal heart rhythms. Beta blockers work by blocking the effects of the endogenous compound epinephrine or adrenaline. Beta blockers order the heart to beat slowly and with less force, leading to reduce blood pressure.

How memory loss can occur with these drugs?

As beta-blockers block crucial chemicals like epinephrine and norepinephrine (important chemical transmitters in the brain) they can lead to memory problems. To avoid this risk of memory impairment some other blood pressure lowering agent should be prescribed especially in older people.

8. Anti-Parkinson drugs

Examples: pramipexole (Mirapex) , apomorphine (Apokyn) , ropinirole (Requip).

Why are these medicines prescribed?

These drugs are used for the treatment of Parkinson’s disease (it is a progressive neurological disease involving loss of neurons in a part of the brain called the substantia nigra), certain pituitary tumors and restless leg syndrome or RLS (in which person has a strong urge to move the legs). These drugs are dopamine agonist. Dopamine is a chemical messenger, which is involved in many functions in the brain, including motivation, learning and memory, fine motor control and the experience of pleasure.

How do they cause memory loss?

Anti-Parkinson drugs increase dopamine levels in the brain by blocking its enzymatic breakdown, and decreased levels of acetylcholine (a neurotransmitter). The reduced level of acetylcholine causes cognitive impairments. Anti-Parkinson drugs may affect those parts of the brain involved in the memory and can cause memory loss as a side effect.

9. Incontinence drugs (anti-cholinergics)

Examples: oxybutynin (Ditropan), oxytrol, darifenacin (enablex), solifenacin (vesicare), trospium (sanctura) and tolterodine (detrol).

Why are these drugs prescribed?

Anticholinergic drugs are incontinence drugs. Incontinence is the inability of the body to control the evacuation functions. It is an emergency situation in which urge to urinate is so strong and sudden that one cannot get to a washroom in time. Anticholinergic drugs are used to relieve symptoms of overactive bladder and reduce episodes of incontinence.

Why memory loss can occur with these drugs?

Anticholinergic drugs block the action of acetylcholine. Acetylcholine is a neurotransmitter (chemical messenger of brain) that mediates all sorts of functions in the body. These drugs prevent involuntary contractions of the muscles controlling urine flow in the bladder. So, in this way anti-cholinergic can decrease incontinence. In the central nervous system these drugs inhibit activity in the learning and memory centers.

When taken for a long time or with other anticholinergic drugs the risk of memory loss is increased. A research conducted in 2006 showed that effects of anti-cholinergic drugs are comparable to 10 years of cognitive aging. That is, these people will have as decrease functions of brain as 10 years more aged people will have. Risk of memory loss is more in older people.

10. Antihistamines (First generation)

Examples: brompheniramine (dimetane), clemastine (tavist), carbinoxamine (clistin), chlorpheniramine (chlor-trimeton), diphenhydramine (bendryl) and hydroxyzine (vistaril).

What is the use of these medicines?

First generation antihistamines are also known as H1 antagonist. They oppose the effects mediated by histamine at H1 receptors. They act by preventing the binding of circulating histamine to its receptor site, but do not inhibit histamine release. Histamine is an endogenous chemical mediator released from some special cells, mast cells, during allergy.

Antihistamines relieve symptoms of common cold, rhinitis, urticaria, asthma and allergy. They reduce wheal formation to an allergen. They are also used to treat motion sickness, nausea, conjunctivitis, vomiting, vertigo, dizziness, anxiety and insomnia.

How do these drugs interfere with memory?

First generation anti-histamines are highly lipid soluble drugs. Only lipid soluble drugs can enter the brain, antihistamines can go into the brain and interfere with normal brain functions.

First generation anti-histamines are potent H1 antagonists, but they are also moderate antagonist of acetylcholine. By lowering acetylcholine they inhibit activity in the brain centers specific for memory, which can lead to memory loss. Now there are some new generation anti-histamines available which produce relatively lesser risks to cognition and memory and are much safer for older people.

11. Tranquilizers (Antipsychotic)

Examples: chlorpromazine (largactil), haloperidol, flupenthixol (fluanxol), pimozide (orap), risperidone (risperdal), clozapine (clozaril), olanzapine (zyprexa), loxapine , quetiapine (seroquel), lithium etc.

Why are these drugs prescribed?

Antipsychotics are particularly used for schizophrenia (it is a mental disorder characterized by a breakdown in thinking and poor emotional responses). They are used for the management of psychosis (abnormal condition of the mind) including delusions, disordered thoughts or hallucinations, and bipolar disorder. They are also used in the treatment of agitation, acute mania and other conditions.

How memory loss can occur with these drugs?

Antipsychotic drugs are the block dopamine receptors in the dopamine pathways of the brain. Dopamine is a neurotransmitter and a hormone. Antipsychotics by blocking dopamine receptors decrease the effects of dopamine in the central nervous system. In addition to dopamine receptors, antipsychotics also depress other receptors including dopamine. Antipsychotics can cause memory loss as their side effect when used for a long time. This is not a common side effect, but can occur in some people taking antipsychotic. Antipsychotic drugs shrink the patient’s brain. Shrinkage of the amygdala, hippocampus and parahippocampus can occur. All these parts of the brain are involved in memory storage and retrieval. Thus, by causing their shrinkage antipsychotics can lead to memory impairment.

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Written by: Michal Vilímovský (EN)
Education: Medical student, 3rd Faculty of Medicine, Charles University, Prague, Czech Republic
Published: April 7, 2014 10:37 AM
Next scheduled update: April 7, 2016 10:37 AM
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